1. Field of the Invention
The present invention relates to the application of water-repellant or hydrophobic coatings on surfaces, particularly polymeric surfaces and most particularly to molded, cast or otherwise shaped polymeric surfaces such as lenses, and most particularly ophthalmic lenses.
2. Background of the Art
The convenience and shaping capability of polymeric materials has been one of its properties that has greatly expanded the field of use and acceptability of polymeric materials into many fields. On the other hand, the limitations in physical properties of polymers, both with regard to abrasion resistance and weathering have limited some of its application.
It is widespread prior art to provide the surfaces of optical components with thin coatings for their protection or in order to obtain certain functional properties. Optical components of this kind are, in the context of this invention, essentially optical lenses, spectacle lenses, and lenses for cameras, field glasses or for other optical apparatus, beam splitters, prisms, mirrors, window panes, etc. On the one hand, the aim of such coatings is to upgrade the surfaces of optical substrates, such that, by means of hardening and/or increasing the chemical resistance, damage caused by mechanical, chemical or environmental influences is avoided. This is particularly significant in the case of substrates comprising plastics materials. On the other hand, surface coatings are employed in order to reduce reflection, especially in the case of spectacle lenses and other lenses. In this context it is possible, given an appropriate choice of the coating materials, coat thickness, single- or multilayer construction comprising, if appropriate, different materials with differing refractive indices, to achieve a reduction in the reflection to less than 1% over the entire visible spectrum of radiation.
Upgrading or antireflection coats of this kind are produced using numerous oxide materials, for instance SiO2, TiO2, ZrO2, MgO2, Al2O3, and also fluorides such as MgF2, and mixtures of these substances. Optical substrates are usually coated by the high-vacuum vapor deposition technique. In this procedure, the substrate and a charge containing the substance to be applied by vapor deposition are placed inside an appropriate high-vacuum vapor deposition apparatus, which is then evacuated, and then the substance is caused to vaporize by heating and/or by means of electron beams, and is deposited on the surface of the substrate as a thin coat. Appropriate apparatus and methods are common prior art.
Upgrading coats of this kind, however, especially antireflection coats, are extremely sensitive to soiling, for example by moist and/or greasy fingerprints. Impurities cause a strong increase in reflection; therefore, fingerprints become clearly visible. Effective cleaning to re-establish the original reflection level proves to be difficult. For this reason, it has become established practice to provide optical components, in addition, with a hydrophobicizing, i.e. water-repellent coating.
For hydrophobicizing the surfaces of optical substrates there is a range of substances available, in particular from the class of organosilicon compounds. These substances are, for example, silanes, siloxanes, silicones and silicone oils (silicone fluids). In general, these substances are applied by dipping or spin coating to the substrate surfaces to be treated, the substances being employed either in pure form or as solutions. Following surface treatment and, if appropriate, evaporation of solvent, a thermal after-treatment is usually carried out, whereby the water-repellent coating is consolidated and adhesion with the substrate material is brought about. In general, this gives coatings with satisfactory properties in respect of hydrophobicization, durability and long-term adhesion.
However, the coating technique necessary as a result of the nature of the customary hydrophobicizing agents is disadvantageous.
For instance, in dip coating and spin coating it is necessary to operate under strict clean-room conditions in order to rule out negative effects on quality, caused, for instance, by dust particles. Furthermore, these techniques require additional operations with corresponding apparatus and plant and may have an increased potential for loss of yield.
JP 05-215 905 discloses a process for preparing water-repellent coatings on optical substrates, which involves the application to the substrate surface of fluoroalkylsilazane compounds by means of a high-vacuum vapor deposition technique. An advantage of this process over the customary dip and spin coating techniques is that it can readily be carried out in existing high-vacuum vapor deposition apparatus, for instance directly after the vapor coating of the substrate with antireflection or other upgrading coats. The perfluoroalkylsilazane compounds are preferably introduced in a form in which a porous metallic sintered material is saturated with the substance.
However, it has been found that the use of polyfluoroalkylsilazane compounds in a high-vacuum vapor deposition process of this kind is disadvantageous. The substances per se are already unstable, which manifests itself in their distinct odor of ammonia. They decompose and are not stable on storage. In the course of vapor coating, the compounds suffer at least partial decomposition, during which ammonia gas is liberated. This causes corrosion in the apparatus and in the associated high-vacuum pumps and also, possibly, on the optical substrates; in addition, there is a risk of reaction of ammonia with the pump oils in the high-vacuum pumps.
U.S. Pat. No. 5,853,800 described a material for and method of preparing water-repellent coatings on optical substrates. The invention relates to a material for and method of preparing water-repellent coatings on optical substrates. Compounds of formula I
CnF2n+1xe2x80x94(CH2)mxe2x80x94Si(R1R2R3)xe2x80x83xe2x80x83(I) 
in which
R1 is alkoxy having 1 to 3 carbon atoms or is CnF2n+1xe2x80x94(CH2)mxe2x80x94Si(R2R3)xe2x80x94Oxe2x80x94,
R2 and R3 are alkyl or alkoxy having 1 to 3 carbon atoms,
n is 1 to 12; and
m is 1 to 6,
are applied to the substrates by thermal vapor coating in a high vacuum from a matrix of inorganic oxides.
U.S. Pat. No. 4,678,688 describes a method for forming a surface film of cured organosilicon polymer on a substrate surface, the polymer comprising units derived from at least one or more monomeric compounds from within the group:
R1aSiO(4xe2x88x92a)/2xe2x80x83xe2x80x83(II) 
R2bSi(N3)O(4xe2x88x92b)/2xe2x80x83xe2x80x83(III) 
R1cXdSiO(4xe2x88x92cxe2x88x92d)/2xe2x80x83xe2x80x83(IV) 
with the respective groups being defined as compositions useful in preparing abrasion resistant coatings for polymeric surfaces.
The invention has discovered a more effective method for the preparation of coatings in high-vacuum vapor coating methods, with the methods producing novel coating compositions with surprisingly increased performance levels over coatings produced from the same materials under different processing conditions. It has now been found that compounds of the general formulae II, III and IV can be applied by vapor deposition from a merely compacted, rather than fused or sintered porous matrix source (as described in U.S. Pat. No. 5,853,800) with improved performance. This improved performance may even occur where the same chemicals are used in the coating, at the same coating temperatures. The generally useful materials include silanes and siloxanes, and siloxazanes of formulae I, II, III and IV:
CnF2n+1xe2x80x94(CH2)mxe2x80x94Si(R1R2R3)xe2x80x83xe2x80x83(I) 
in which
R1 is alkoxy having 1 to 3 carbon atoms or is
xe2x80x83CnF2n+1xe2x80x94(CH2)Smxe2x80x94Si(R2R3)xe2x80x94Oxe2x80x94
R2 and R3 are alkyl or alkoxy having 1 to 3 carbon atoms,
n is 1 to 12 and
m is 1 to 6; and
organosiloxazanes, such as those comprising polymers derived from at least one, and preferably combinations of two or more monomers, each one selected from a different formula, wherein the monomers may be of the formulae:
R1aSiO(4xe2x88x92a)/2xe2x80x83xe2x80x83(II) 
R2bSi(NR3)O(4xe2x88x92b)/2xe2x80x83xe2x80x83(III) 
R1cXdSiO(4xe2x88x92cxe2x88x92d)/2xe2x80x83xe2x80x83(IV) 
wherein in the unit formulae (II and IV) for the organosiloxane unit, R1 is a hydrogen atom or a monovalent hydrocarbon group exemplified by alkyl groups such as methyl, ethyl, propyl and butyl groups, aryl groups such as phenyl and tolyl groups, alkenyl groups such as vinyl and allyl groups and cycloalkyl groups such as cyclohexyl group as well as those substituted hydrocarbon groups obtained by the replacement of a part or all of the hydrogen atoms in the above named hydrocarbon groups with substituent atoms or groups such as halogen atoms and cyano groups. The groups denoted by R1 in a molecule may not be of the same kind but two or more kinds of the groups can be contained in a molecule although it is preferable that not all of the groups R1 in a molecule are hydrogen atoms. The subscript a is 1, 2 or 3 to give tri-, di- and monofunctional siloxane units, respectively. R2 is a hydrogen atom or a monovalent hydrocarbon group exemplified by alkyl groups such as methyl, ethyl, propyl and butyl groups, aryl groups such as phenyl and tolyl groups, alkenyl groups such as vinyl and allyl groups and cycloalkyl groups such as cyclohexyl group as well as those substituted hydrocarbon groups obtained by the replacement of a part or all of the hydrogen atoms in the above named hydrocarbon groups with substituent atoms or groups such as halogen atoms and cyano groups. R3 may be an aliphatic or aromatic hydrocarbon group such as methyl, ethyl, propyl and butyl groups, aryl groups such as phenyl and tolyl groups, alkenyl groups such as vinyl and allyl groups and cycloalkyl groups such as cyclohexyl group as well as those substituted hydrocarbon groups obtained by the replacement of a part or all of the hydrogen atoms in the above named hydrocarbon groups with substituent atoms or groups such as halogen atoms and cyano groups.
As is mentioned above, the monovalent hydrocarbon group denoted by R1 may be at least partially substituted by various kinds of substituent atoms and groups according to the particular curing behavior of the polymer and performance and properties desired of the resultant polymer and the cured product thereof. Some of the substituents include halogen atoms, alkoxy groups such as methoxy and ethoxy groups, amino group, cyclohexylamino group, oxime group, epoxy group, acryloxy group, methacryloxy group and the like. Particular examples of such substituted hydrocarbon groups include those expressed by the formulas CF3CH2CH2xe2x80x94, Gl-Oxe2x80x94CH2)3xe2x80x94, CH2xe2x95x90CHCOO(CH2)3xe2x80x94, CH2xe2x95x90CMeCOO(CH2)3xe2x80x94, and NH2(CH2)3, in which the symbols Me and Gl denote a methyl and a glycidyl group, respectively.
The units of the other type essentially contained in the molecule of the organosiloxazane polymer in combination with the above described organosiloxane units are the organosilazane units represented by the unit formula (III) above given, in which R2 and R3 are each a hydrogen atom or a monovalent hydrocarbon group selected from the class consisting of the above named groups given as the examples of the hydrocarbon groups for R1 in the unit formula (II) although not all of the groups R2 in a molecule are preferably hydrogen atoms. Several examples of the units in conformity with the formula (II) include: MeSi(NH)1.5; CH2xe2x95x90CHSi(NH)1.5, EtSi(NH)1.5, nxe2x80x94C10H21Si(NH)1.5; (CF3)2CF(CF2)8CH2CH2Si(NH)1.5; PhSi(NH)1.5; Me(MeO)Si(NH)1.0; Me(MeEtCxe2x95x90NO)Si(NH)1.0; CH2xe2x95x90CMeCOO(CH2)3(OMe)Si(NH)1.0; and NH2(CH2)3Si(NH)1.5, in which the symbols Me, Et and Ph each denote a methyl, an ethyl and a phenyl group, respectively.
With regard to Formula IV, R1 has the same meaning as defined above, R4 is a divalent hydrocarbon group exemplified by alkylene groups such as ethylene, propylene and butylene groups and arylene groups such as phenylene and tolylene groups, e is zero, 1 or 2, f is zero, 1 or 2, g is 1, 2 or 3 with the proviso that f+g is not larger than 4 and m, n and p are each a positive integer. X is a halogen atom, e.g., Fl, Cl, Br and I, preferably Cl. The chlorine-containing organosilicon compound (ii) to be reacted with the above described chlorine-containing organopolysiloxane (i) is preferably a silane or polysilane compound and suitable silane compounds therefor are exemplified by those compounds expressed with the following formulas including:
R2hSiX4xe2x88x92h; 
X3xe2x88x92eR2eSi"Brketopenst"SiR22O"Brketclosest"m"Brketopenst"SiX R2"Brketclosest"n"Brketopenst"SiX2"Brketclosest"pSiR2eX3xe2x88x92e; 
and 
X3xe2x88x92eR2eSiR4"Brketopenst"SiR22R4"Brketclosest"m"Brketopenst"SiClR2R4"Brketclosest"n"Brketopenst"SiX2R4"Brketclosest"pSiR2eCl3xe2x88x92e; 
R2iSi"Brketopenst"OR2"Brketclosest"jX4xe2x88x92ixe2x88x92j; 
in which h is zero, 1, 2 or 3, i is zero, 1, 2 or 3 and j is zero, 1, 2 or 3 with the proviso that i+j is 1, 2 or 3, X is a halogen atom (e.g., Cl, Br, F, and I, preferably Cl) and R2, R4, e, m, n and p each have the same meaning as defined above.
These compounds are ideally suited to the preparation of water-repellent coatings on optical substrates by thermal vapor coating, preferably in a high vacuum, preferably from a non-sintered porous source for the silicon containing material.